Chemistry: electrical current producing apparatus – product – and – Plural concentric or single coiled electrode
Reexamination Certificate
1999-11-15
2002-01-01
Maples, John S. (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Plural concentric or single coiled electrode
C429S161000, C429S162000, C429S211000, C429S217000, C429S245000
Reexamination Certificate
active
06335114
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the technical field of laminate-type batteries such as coiled electrode batteries, and of manufacturing processes for electrodes that can be employed in such laminate-type batteries.
2. Description of the Prior Art
As lithium ion secondary batteries with high energy density per unit volume and per unit weight have become commonly used as power sources for cellular telephones, portable video cameras, portable data terminals and the like, attention is also being focused on their use as batteries for electric automobiles.
When lithium ion secondary batteries are used for electric automobiles, however, the requirement to provide high power has presented problems of heat generation and insufficient output because of the high internal resistance of the batteries in the commonly employed system of current output through tabs. That is, it has been difficult and thus inconvenient to achieve high output by current collection from coiled electrodes with simple tabs. However, when it is attempted to weld multiple tabs to coiled electrodes, the multiple tabs become welded to the coiled electrodes during coiling, resulting in the inconvenience of low productivity as the number of steps in the coiling process is increased.
With the aim of eliminating this inconvenience, Japanese Unexamined Patent Publication No. 55-80269 has disclosed a coiled electrode battery which is based on the prior art.
This coiled electrode battery has a coiled formed by electrode coiling both a belt-like positive plate and negative plate having protrusions protruding out along the axial length of the coil in opposite directions to each other, and a separator lying between the positive plate and negative plate. That is, both the positive plate and negative plate have a protrusion protruding out from the edges of each electrode plate of with opposite polarity (opposite polarity plates). The positive plate and negative plate have respective collectors welded thereto, and the positive plate and negative plate are connected through these collectors to a pair of positive
egative electrode terminals that supply external power.
Thus, the coiled electrode batteries of the prior art require no connection of multiple tabs and can therefore be produced without sacrificing productivity, while their collectors with low electrical resistance allow them to exhibit large output without the risk of overheating.
Nevertheless, with the aforementioned coiled electrode battery of the prior art, it has been difficult to achieve production at high yields because the protrusions contact with the edges of the opposite polarity plates due to misaligned winding of the separator, producing short-circuits. For example, if the positions of the positive plate, negative plate and separator do not precisely match in the axial length direction of the coil, the opposite edge which is in the opposite direction from the protrusions will contact the adjacent protrusions of opposite polarity, causing a short-circuit. Since short-circuits can be easily caused by contact between the opposite edge of the negative plate and the protrusion of the positive plate when the separator is misaligned, the defect rate has often been significantly high in the production process.
This sort of problem is not limited to coiled electrode batteries but can also occur with other laminate-type batteries of the prior art, for example, batteries equipped with laminated electrodes prepared by forming disk-shaped positive plates and negative plates laid together with a separator between them, such as coin-type batteries, and batteries equipped with laminated electrodes formed by alternately laminating square-shaped positive plates and negative plates with separators between them, such as square batteries.
That is, even in these laminate-type batteries, if the alignment positions of the positive plate, negative plate and separator do not precisely match, the opposite edge which is in the opposite direction from the protrusion can contact the adjacent protrusion of opposite polarity, causing a short-circuit. As a result, since short-circuiting can easily occur, for example, if the opposite edge of the negative plate exposed by misalignment of the separator contacts with the protrusion of the positive plate, similar to the coiled electrode battery mentioned above, the reject rate has often been significantly high in the production process. Consequently, it cannot be said that laminate-type batteries of the prior art offer sufficiently high product yields.
On the other hand, all batteries of the prior art are susceptible to shrinkage of the separator upon abnormal increase of temperature in the battery during use. The possibility also exists that vibrations, etc. will cause the separator to shift from the prescribed position between the positive plate and negative plate. In these cases as well, the protrusions of the positive plate and negative plate which protrude out beyond the edges of the opposite polarity plates can produce short-circuits by contacting with the edges of the opposite polarity plates.
It is therefore an object of the invention to provide a laminate-type battery that can reliably prevent short-circuiting inside the battery and which allows higher product yields.
It is another object of the invention to provide an electrode-manufacturing process that can be used for such a laminate-type battery and that allows easy manufacture of electrodes.
SUMMARY OF THE INVENTION
The present inventors have invented the following means in order to achieve these objects.
(First aspect)
The first aspect of the invention is a laminate-type battery with a laminated electrode prepared by laminating a sheet-like positive plate and negative plate and a separator lying between the positive plate and the negative plate, characterized in that at least either one of the positive plate and the negative plate has a protrusion that protrudes out beyond the edge of the other electrode plate of opposite polarity (opposite polarity plate), and the protrusion has a short-circuit preventing layer on the surface of at least its proximal section. The protrusion may be a conductor formed separately from the electrode and bonded to the electrode plate, or it may be formed integrally with the electrode. It is particularly preferred for the protrusion to protrude from the edge of the opposite polarity plate which is adjacent to it via the separator.
According to this aspect, the laminate-type battery which allows contact between the electrode plate with the protrusion and the non-protruding edge (non-protruding section) of the opposite polarity plate, is provided with a short-circuit preventing layer at the proximal section of the protrusion. Consequently, even if the non-protruding section contacts with the proximal section of the protrusion due to lamination misalignment of the separator when the positive plate and negative plate are laminated, the presence of the short-circuit preventing layer lying between the non-protruding section and the proximal section of the protrusion prevents short-circuiting between the positive and negative poles. In addition, when there is a risk of the non-protruding section contacting with the protrusion due to burrs on the non-protruding section, short-circuiting between the positive and negative poles is prevented in the same manner by the short-circuit preventing layer situated at the proximal section of the protrusion.
According to this aspect, therefore, short-circuiting between the positive and negative poles in the battery can be reliably prevented for an effect which allows laminate-type batteries to be provided at higher product yields.
With this aspect, the external leads of the device to which the power from the battery is to be supplied can be directly connected to the positive plate and negative plate of the laminate-type battery, but for the purpose of increasing the power current-collecting efficiency and sealing of the electrolyte solution, it is preferred to provide a
Amano Tadayoshi
Hosokawa Norikazu
Kami Kenichiro
Shinkai Ryuichirou
Ueshima Hiroshi
Denso Corporation
Maples John S.
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